1. Field of the Invention
The invention described herein relates to an apparatus and a method for growing suspension and adherent cells in vitro.
2. Background Art
Growing living cells in vitro is performed for a variety of purposes, including the production of cell derivatives, the preparation of viral vaccines, and the recovery of valuable cell by-products. Among the devices that have been developed for growing cells in vitro, the shell-and-tube type arrangement has become fairly common, particularly for growing suspension and adherent cells.
These devices use semipermeable tube-shaped hollow fibers (i.e., capillaries), contained within an outer shell, and configured so that fluid within a space external to the hollow fibers (i.e., an extra-capillary space) is segregated from fluid passing through the hollow fibers and their corresponding openings (i.e., lumens). Additionally, these devices usually include two manifold end chambers within the outer shell on opposite ends of the device. Each of the two lumens of a hollow fiber connects to a different end chamber. The end chambers and the extra-capillary space are separated by the semi-permeable membranes of the hollow fibers. The composition of the extra-capillary space can be controlled, to a certain extent, by the molecular weight cutoff, or pore size, of the membranes of the hollow fibers.
Typically, cells are grown in the extra-capillary space while a nutrient media is passed through the hollow fibers. The semipermeable nature of the hollow fibers allows nutrients and cell waste products to pass through the walls of the hollow fibers while blocking cells from doing the same. U.S. Pat. No. 4,391,912 to Yoshida et al. specifies a range of pore diameters to support the transfer of the nutrient medium from the intra-capillary to the extra-capillary space while blocking the entrance of cells into the intra-capillary space.
Shell-and-tube type bioreactors provide several advantages. For adherent cells, the use of several hollow fibers provides, within a relatively small volume, a large amount of surface area upon which the cells can grow. For both suspension and adherent cells, this large amount of surface area also facilitates localized distribution of nutrient media to the growing cells and ready collection of cell waste products. Shell-and-tube type bioreactors enable the growth of cells at much higher density rates than is possible with other cell culture devices. They can support cell densities greater than 108 cells per milliliter, whereas other cell culture devices are typically limited to densities around 106 cells per milliliter.
However, existing designs typically require external support systems to circulate the nutrient media through the hollow fibers. U.S. Pat. No. 3,883,393 to Knazek et al., U.S. Pat. No. 4,144,136 to Corbeil, U.S. Pat. No. 4,391,912 to Yoshida et al., U.S. Pat. No. 5,290,700 to Binot et al., and U.S. Pat. No. 5,955,353 to Amiot, all teach systems in which the nutrient medium is supplied to the intra-capillary spaces using pumps and associated connection tubing. These external circulating systems add considerably to the cost of using these types of shell-and-tube bioreactors.
What is needed is a shell-and-tube type apparatus to grow suspension and adherent cells that does not require an external circulating system for the nutrient media fluid.